Apparatus for testing and recording the freeness of fiber suspension



R. B. RE|NHALL 3,330,151 FOR TESTING AND RECORDING THE FREENESS July l1, 1967 APPARATUS OF FIBER SUSPENSION Filed Jan. 21, 1964 United States Patent O 3,330,151 APPARATUS FOR TESTING AND RECORDING THE FREENESS F FIBER SUSPENSION Rolf Berti] Reinhall, Lidingo, Sweden, assigner to Deibrator Aktiebolag, a corporation of Sweden Filed Jan. 21, 1964, Ser. No. 339,240 Claims priority, application Sweden, Jan. 22, 1963, 688/63 2 Claims. (Cl. 73-63) This invention relates to a device for testing and recording the water releasing properties of a solid material dispersed in an aqueous suspension, primarily lignocellulose containing bers in a pulp or stock intended for the making of paper or board. This fibrous suspension, for example, is denominated in the cellulose industry as the freeness of the stock and means a measure or r-ate to determine how quickly the brous suspension is released of water on the web forming part of a paper-making machine, -for example.

Most apparatus used in laboratories which are obtainable in the market and intended to record a measure or rate of this freeness operate with a predetermined quantity of fibers dispersed in a predetermined quantity of water which suspension has been introduced into a vessel provided with a bottom of screen or wire gauze of varying size depending on the water release range to be tested. In the tests of this type either the time is measured which elapses for the passage of the water through the ber mat accumulated on the screen bottom or the speed of the water passing through said mat is measured so as thereby to obtain an indication for the water releasing ability of the pulp or stock.

One main object of the invention is to replace laboratory apparatus by a continuously or periodically operating apparatus mounted in direct connection to the inlet and/ or outlet of stock treating machines where there is a desire of recording or determining the results of the treatment in progress.

Further objects and advantages of the invention will become apparent from the following description considered in connection with the accompanying drawing of an embodiment vof the invention shown in diagrammatic side elevation partly in vertical longitudinal section.

Referring to the drawing, reference numeral denotes a preferably cylindrical casing which at its top may be closed by a cover 12 and which at its bottom has a discharge 14. Located within said casing is a preferably cylindrical container 16 having a smaller diameter than said casing and continuing downwardly with a preferably conically tapering portion 18 through which it is connected with a supply conduit 2G for a pulp suspension in the form of fibers dispersed in water. The fiber stock may come from a grinding apparatus (not shown) the concentration of the liber stock in the suspension being regulated to a constant value prior to the entry of the suspension into the container 16 by means known per se and therefore not described more detailed in the present connection. The container 16 is open at its upper edge and the pulp suspension supplied thereto is lallowed to escape undisturbed using said edge as a spill-over dam as is indicated in the drawing so that a constant level is maintained in the container 16.

A measuring vessel 22 of preferably cylindrical form is at its base provided with a screen bottom 24. In the embodiment shown the measuring vessel 22 is axially displaceable relatively to the container 16 by means of a servo-cylinder 26 and a piston 28 which is adapted to reciprocate therein, and having a piston rod 30 secured to a cover 32 on the vessel 22. An assembly 34 for hydraulic or pneumatic operation with valves of known type suitably actuated by electricity is in connection with the two ends of the cylinder 26 through conduits 36, 38 of exible material. By means of this arrangement the measuring vessel 22 can be displaced from a position with the screen bottom 24 above the level of the pulp in the container 16 to a position of immersion Within said container.

A flushing device comprises a supply conduit 40 for flushing water, said conduit being connected to conduits 42 which through their open lower ends communicating with the interior `of the Vessel 22 and which pass undisturbed through the cover 32 of said vessel. The conduit 40 is controlled by a valve 44 the body of which is actuated by a control unit 46 which in turn as well as the assembly 34 operates in response to impulses received from a change-over `switch 48 in accordance with a programme determined by said switch.

The servo-cylinder 26 is connected with a plate 50 which in turn is mounted on an electric transmit-ter 52 of a type known per se, such as for example, the piezo type which via said plate records those variations in lifting capacity to which the measuring vessel 22 is subjected when being immersed into the container 16 in a manner to be explained in more detail hereinafter. The electric transmitter S2 transmits the impulses received through an amplifier S4, for example, to a recording instrument 56. Said instrument has a window 58 behind which a paper strip is visible and on which the impulses arriving to the instrument are recorded as is indicated by line 60.

The apparatus operates in the following manner. Through an impulse from the change-over switch 48 pressure fluid is supplied to the upper side of the piston 28 in 'the cylinder 26 causing the measuring vessel 22 to be moved downward substantially to the position in the y container 16 shown in the drawing. Under this movement the valve 44 is closed. The displacement speed of the vessel 22 in both directions is relatively constant for the same kind of recording. When the screen bottom 24 is pushed below the pulp level in the container 16, suspension tends to penetrate into the vessel 22 whereunder a layer or mat xof libers accumulates on the lower side of the screen bottom, said ber layer being water-permeable so as to allow water released from the bers to ow into the interior of the measuring vessel 22. The rate at which the water level in the measuring vessel rises is dependent `on the freeness of the stock. lf now the measuring vessel is in its lowered position during a period of time which is adjustable -but constant for each course of manufacture the vessel will due to the upwardly directed pressure of the suspension be lled with water to a predetermined level more or less rapidly. The rate of the rising of the water Within the measuring vessel is dependent on the more or less eifective sealing ability of the deposited bers which constitutes a measure of their freeness. The measuring vessel 22 in its immersed position will thus be subjected to an upwardly directed lifting force the magnitude of which at every instant is determined by the difference in the levels of the liquid in the measuring vessel 22 and the container 16, respectively. The upwardly directed lifting force reduces the pressure exerted by the servo-cylinder 26 and the parts of the apparatus carried by said cylinder on the electric transmitter 52 which in turn by means of the recording instrument records the course. The lifting force acting on the measuring vessel 22 will thus be recorded by the instrument 56 and thus give a direct recording `of the capacity of permeability to water of the fiber layer which deposits on the lower side of lthe screen bottom 24 and which is in direct relation to the freeness =of the stock.

When the measuring vessel 22 has been kept in its lowered position for a predetermined period, the changeentirely to remove the layer of'ibers from the screen bottom V24. The flushing water causes a partial dilution of the suspension contained in the container 16 for which reason some time must elapse until the next measuring operation may take place when the stock concentration due to the continuous supply to, and discharge from, the container has regained its constant value.

It is obvious `from the explanations hereinbefore that VVnot -only the absolute variation of the liquid level within the measuring vessel according to the invention can be read but also the speed or rate with which the liquid rises in the interior of the measuring vessel. The recording inf strument 56 is capable besides of showing the actual freeness of the pulp to indicate also such properties as the content ofthe fibrous suspension of differentrber sizes which altogether render to the stock a certain permeability to water but which individually are capable of iniluencing the decreasing speed with which the liquid rises in the interior of the measuring vessel.

The cycle of operations of the apparatus may be adjusted by means of the change-over switch 48 within Wide limits sogas to be suited to the most diiferent kinds of brous suspensions. Both the lowering speed and the stay of the measuring device 22 in the upper and lower position, respec-tively, may be controlled and`guided automatically, for example by means of an electric synchronic programming emitter. In order to eliminate or at least considerably reduce sources of errors during the ow o f the pulp suspension the ow area in the outer container 16 should be made'relatively great in relationship to the flow area in the measuring vessel 22. The speed of flow of the ber suspension through the outer container should be low.

The measuring impulse emanating from the transmitter 52 may besides being used for recording of variations also be transformed so as directly and automatically to control one or several liber treatingmachines through which the stock in the conduit 20 has passed so as to cause said machines continuously to treat the -brous suspension so as to attain a desired constant freenessr While one more or less specific embodiment of the invention has been shown and described, it is to be understood that this is for purpose of illustration only and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.

What I claim is:

1. An apparatus for testing and recording the freeness of uid paper stock comprising a constant level ow container, means for passing the paper stock to be tested in a ow path through said container, an immersion typeV tubular testing vessel comprising an imperforate peripheral Wall and a bottom screen Wall which is directed against the flow path of said fluid, means for periodically reciprocating said testing vessel between a position above the paper stock level and an immersed position in said container to a fixed depth in the paper stock, and recording means directly responsive to the variable upwardly directed force exerted on the bottom screen walllcaused by the accumulation of solid'paper stock particles on said bottom screen while free fluid is admitted by said screen into said testing vessel. Y

2. Apparatus according to claim 1 wherein said recording means is actuated by piezo electric impulse means connected to said testing vessel and impulsed by pressure caused by the force acting on said vessel.

References Cited DAVID SCHONBERG, Primary Examiner. 

1. AN APPARATUS FOR TESTING AND RECORDING THE FREENESS OF FLUID PAPER STOCK COMPRISING A CONSTANT LEVEL FLOW CONTAINER, MEANS FOR PASSING THE PAPER STOCK TO BE TESTED IN A FLOW PATH THROUGH SAID CONTAINER, AN IMMERSION TYPE TUBULAR TESTING VESSEL COMPRISING AN IMPERFORATE PERIPHERAL WALL AND A BOTTOM SCREEN WALL WHICH IS DIRECTED AGAINST THE FLOW PATH OF SAID FLUID, MEANS FOR PERIODICALLY RECIPROCATING SAID TESTING VESSEL BETWEEN A POSITION ABOVE THE PAPER STOCK LEVEL AND AN IMMERSED POSITION IN SAID CONTAINER TO A FIXED DEPTH IN THE PAPER STOCK, AND RECORDING MEANS DIRECTLY RESPONSIVE TO THE VARIABLE UPWARDLY DIRECTED FORCE EXERTED ON THE BOTTOM SCREEN WALL CAUSED BY THE ACCUMULATION OF SOLID PAPER STOCK PARTICLES ON SAID BOTTOM SCREEN WHILE FREE FLUID IS ADMITTED BY SAID SCREEN INTO SAID TESTING VESSEL. 